Androecium basically of two whorls of stamen fascicles, the outer (antisepalous) one often sterile (fasciclodes) or absent, filaments variously united or free (when the androecium may appear polyandrous); antipetalous fascicles variously united or free, very rarely each one reduced to a single stamen

Terrestrial or hemiepiphytic trees, shrubs or lianas, frequently with adventitious roots ; usually glabrous and evidently laticiferous ; exudate mostly white to yellow, sometimes orange, rarely clear or not evident. Leaves simple , exstipulate , entire and usually opposite, with laticifers or glands . Inflorescences terminal or axillary , cymose or less commonly racemose. Flowers hermaphroditic or unisexual (plants then mostly dioecious ), with pedicel often with one or more pairs of bracteoles, these sometimes similar to or grading into sepals. Sepals (2-)4-many, usually free (though may be joined at base). Petals 4-9, often white or cream, less often green, pink, red, orange, purple or blackish. Androecium extremely variable, consisting of 4 to several hundred stamens that may be fused into fascicles or synandria of varying shape, not uncommonly accompanied by staminodes and frequently secreting resin or oils. Ovary superior and syncarpous, consisting of 2-8(-20) carpels, often surrounded by staminodes. Styles 1-8 or stigma sessile . Fruit a dry or fleshy capsule or a berry , rarely a drupe . Seeds often arillate.

Apocynaceae may be vegetatively similar to some Clusiaceae, but have abundant, fast-flowing latex.

Caraipa, Mahurea and Kielmeyera have alternate leaves and sparse latex and may be confused with a number of other families, e.g. the Bonnetiaceae, which completely lack latex, and the Sapotaceae which have latex, and sometimes similar venation and even occasionally opposite leaves, but can be distinguished vegetatively based on the presence of T-shaped hairs.

Other important characters

Most Clusiaceae have a tendency to form adventitiousroots.

White to yellow latex.

Coriaceous opposite leaves.

Parallel secondary and intersecondary veins.

Many stamens, often variously fused.

Notable genera and distinguishing features

Clusia (over 400 spp. all Neotropical). Widespread hemiepiphytes, lianas, small trees and shrubs with fleshy capsules and seed less than 6 mm long with an orange aril. Flowers often with resin.

Chrysochlamys (over 60 spp. all Neotropical). Common understorey treelets in rainforests. Like Clusia but usually ramiflorous, and seeds ca 10 mm long.

Clusiaceae are members of the large and heterogeneous order Malpighiales.

The two subfamilies Clusioideae and Kielmeyeroideae are well supported groups, but with few uncontradicted characters uniting them.

The Hypericaceae have often been included in Clusiaceae, but have recently been shown to be more closely related to Podostemaceae.

General notes

The family occurs in most Neotropical habitats, from sea level to 3,500m altitude (spp. of Clusia). Diversity of genera is highest on the Guayana shield and surrounding areas whereas species diversity is highest in and near the Northern Andes.

The West Indies are poor in species.

Most species are found in rainforests but species of Clusia, Garcinia and Kielmeyera also occur in dry, open habitats (Clusia then often with almost succulent leaves and Garciniasclerophyllous with spine -tipped leaves).

Gentry, A. H. 1993. A Field Guide to the Families and Genera of Woody Plants of Northwest South America (Colombia, Ecuador, Peru) with supplementary notes on herbaceous taxa. The University of Chicago Press, Chicago.

Stamens usually numerous, free or very often in fascicles or fused into groups, anthers usually with 2 thecae dehiscing by longitudinal slits; the outer fascicles are often sterile “fasciclodes”, frequently forming what is often called the disc, or are absent

Gynoecium

Ovary superior, 1–several-locular, with parietal, axile, apical or basal placentation; ovules anatropous, l–? per locule; styles free or fused, sometimes very short or absent; stigmas or stigma-lobes mostly equal in number to the locules

Fruits

Fruit a berry, drupe or septicidal (rarely loculicidal) capsule

Seeds

Seeds arillate or not, without albumen, sometimes winged; embryo with cotyledons often very reduced